There are roughly between 250 and 300 species of plants in the senna family, but S. alexandrina is attributed as the source of senna leaf and senna pods. With the exception of Europe, the plant thrives in the tropical and subtropical regions of every continent in the world. It is grown extensively as a commercial crop in southern Egypt and northern Sudan, where the herb is a significant source of income to farmers and distributors. The plant is harvested twice each year, dried in the sun and transported to ports along the Red Sea via camel caravans.
Senna contains senna glycosides, which are derivatives of an organic compound with known laxative properties called anthracenedione. These anthracene derivatives are collectively referred to as sennosides and further identified as sennosides A, A1, B, C and D.
